1. Field of the Invention
This invention relates broadly to surgery. More particularly, this invention relates to orthopedic fasteners.
2. State of the Art
According to recent trends, there is a need to reduce the profile of bone plates and screws for internal fixation of fractured bones. This is especially important for plates used to repair fractures of the elbow, which has relatively little protection by overlying soft tissues and is highly vulnerable, for example, to accidental bumping as the fracture heals. Development of very thin, anatomically conforming bone plates has created new challenges related to plate-to-bone attachment. More specifically, improved designs for fastener systems are needed so that minimal implanted hardware protrudes undesirably above the top surface of the plate and irritates and/or inflames the overlying tissues.
In general, there is also a need to reduce the inventory of bone screws required for internal fixation procedures due to the high cost of providing and maintaining a sterilizable surgical kit containing a large quantity of different screw sizes and types for the varied patient anatomies and fracture types.
There have been developed bone screws and retainable (or captive) washers that attach to the screw head. However, the focus on such prior systems apparently was not to provide a low profile screw and washer assembly for use on bone plates that are thinner than previous, conventional bone plates. Nor was emphasis placed on providing a bone screw that may be used for multiple functions, thereby reducing the required inventory of screws required for a surgical procedure.